MC9S12E128CPV Freescale Semiconductor, MC9S12E128CPV Datasheet - Page 292

• Manufacturer Part Number: MC9S12E128CPV
• Description: Microcontrollers (MCU) 16 Bit 16MHz
• Manufacturer: Freescale Semiconductor

Specifications of MC9S12E128CPV

• Data Bus Width: 16 bit
• Program Memory Type: Flash
• Program Memory Size: 128 KB
• Data Ram Size: 8 KB
• Interface Type: SCI, SPI
• Maximum Clock Frequency: 25 MHz
• Number Of Programmable I/os: 92
• Number Of Timers: 16 bit
• Operating Supply Voltage: 3.135 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: LQFP-112
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 10 bit
• On-chip Dac: 8 bit, 2 Channel
• Lead Free Status / Rohs Status: No RoHS Version Available

Chapter 9 Serial Peripheral Interface (SPIV3)
In master mode, with slave select output enabled the SS line is always deasserted and reasserted between
successive transfers for at least minimum idle time.
9.4.3.3
Some peripherals require the first SCK edge before the first data bit becomes available at the data out pin,
the second edge clocks data into the system. In this format, the first SCK edge is issued by setting the
CPHA bit at the beginning of the 8-cycle transfer operation.
The first edge of SCK occurs immediately after the half SCK clock cycle synchronization delay. This first
edge commands the slave to transfer its first data bit to the serial data input pin of the master.
A half SCK cycle later, the second edge appears on the SCK pin. This is the latching edge for both the
master and slave.
When the third edge occurs, the value previously latched from the serial data input pin is shifted into the
LSB or MSB of the SPI shift register, depending on LSBFE bit. After this edge, the next bit of the master
data is coupled out of the serial data output pin of the master to the serial input pin on the slave.
This process continues for a total of 16 edges on the SCK line with data being latched on even numbered
edges and shifting taking place on odd numbered edges.
Data reception is double buffered, data is serially shifted into the SPI shift register during the transfer and
is transferred to the parallel SPI Data Register after the last bit is shifted in.
After the 16th SCK edge:
Figure 9-10
slave timing diagram because the SCK, MISO, and MOSI pins are connected directly between the master
and the slave. The MISO signal is the output from the slave, and the MOSI signal is the output from the
master. The SS line is the slave select input to the slave. The SS pin of the master must be either high or
reconfigured as a general-purpose output not affecting the SPI.
The SS line can remain active low between successive transfers (can be tied low at all times). This format
is sometimes preferred in systems having a single fixed master and a single slave that drive the MISO data
line.
In master mode, if a transmission has completed and a new data byte is available in the SPI Data Register,
this byte is send out immediately without a trailing and minimum idle time.
The SPI interrupt request flag (SPIF) is common to both the master and slave modes. SPIF gets set one
half SCK cycle after the last SCK edge.
292
•
•
•
Data that was previously in the SPI Data Register of the master is now in the data register of the
slave, and data that was in the data register of the slave is in the master.
The SPIF flag bit in SPISR is set indicating that the transfer is complete.
Back-to-back transfers in master mode
shows two clocking variations for CPHA = 1. The diagram may be interpreted as a master or
CPHA = 1 Transfer Format
MC9S12E128 Data Sheet, Rev. 1.07
Freescale Semiconductor